7.12.2. Enabling Seam exception handling

To enable Seam's exception handling, the master Servlet filter must be declared in web.xml: 
<filter> 
  <filter-name>Seam Filter</filter-name> 
  <filter-class>org.jboss.seam.servlet.SeamFilter</filter-class>
</filter> 

<filter-mapping> 
  <filter-name>Seam Filter</filter-name> 
  <url-pattern>*.seam</url-pattern> 
</filter-mapping>
For the exception handlers to fire, you must disable Facelets development mode in web.xml and Seam debug mode in components.xml.